In a fin field-effect transistor (FinFET), current leakage in a region below a channel region of the FinFET in a bottom portion of a fin structure should be prevented or suppressed.
To reduce current leakage, a Silicon-On-Insulator (SOI) substrate, which is much more expensive than a traditional silicon substrate, may be used such that a buried oxide layer of the SOI substrate can be used to isolate the source and drain regions.
Alternatively, a punch-through stopper or an oxide layer may be buried below the channel region so as to increase resistivity thereof, thereby reducing current leakage. However, forming a punch-through stopper below the channel region and forming an oxide layer below the channel region are complicated and difficult to control.